week 2 Flashcards
Describe 3 theories of ageing
Rate-of-Living Theories
Cellular Theories
Programmed cell death theories
What is ageing?
The accumulation of changes in a human being over time; physical, psychological and social
‘The collection of changes that render human beings progressively more likely to die’ (Medawar, 1952)
After our sexual peak (about 30), our chances of dying double approximately every 8 years (MDRT)
The rate of ageing and the MRDT are thought to have remained unchanged for thousands of years
The mortality rate (IMR) has been lowered – meaning an increase in lifespan and longevity
What is ageing? (3 things)
Primary ageing is normal, disease-free development during adulthood.
Secondary ageing is developmental changes that are related to disease, lifestyle, and other environmentally induced changes that are not inevitable (e.g., pollution).
Tertiary ageing is the rapid losses that occur shortly before death
What is MRDT?
Mortality Rate Doubling Time:
After our sexual peak (about 30), our chances of dying double approximately every 8 years
What is IMR
the initial mortality rate
the mortality rate independent of aging, often calculated from the mortality rate prior to its exponential increase with age;
What happened last century was that the IMR, which is not affected by the aging rate, was lowered due to breakthroughs in different areas, such as in the war against infectious diseases, thus lowering mortality rates across the entire lifespan and increasing the life expectancy. Because the increase in life expectancy was due to changes in the IMR independent of changes in aging rates is also the reason why the average lifespan of humans may be reaching a plateau.
Reasons why we age
Programmed factors - ageing follows a biological timetable which is driven by genetically regulated processes
Damage-related factors - ageing results from a continuous process of damage accumulation originating in by-products of metabolism
Rate-of-Living Theories
The faster an your metabolism, the shorter your lifespan
- Limited energy
- Hormonal regulatory system adaptation to stress
- Excess calories
Cellular Theories
Limited number of times a cell can divide Hayflick limit
-Telomeres and the enzyme telomerase
Wear and tear
-Tissues become worn out
Cross-linking
-Tissue becomes stiffer with age
Free radicals
-Reactive chemicals causing cellular damage
Programmed cell death theories
Aging may be programmed into genetic code
Cells pre-programmed to self-destruct
-Apoptosis- genetically motivated process ofprogrammed cell death where acell iscarefully sectionalized and its fragments can beused byother cells asabuilding material
Genes and ageing
Genes can increase or decrease longevity in complicated ways
A single gene mutations in worms can extend lifespan by almost 10-fold
There is a significant degree of heritability of longevity, in particular at later ages
The offspring of long-lived parents are protected against age-related diseases
Progeroid syndromes
Rare genetic diseases that manifest in ‘accelerated ageing’
Werner’s (WS), Cockayne, and Hutchinson-Gilford’s (progeria) syndrome
Ageing is a complex process composed of several features:
An exponential increase in mortality
Physiological changes that typically lead to a functional decline with age
Increased susceptibility to certain diseases
Life Expectancy:
How long one is expected to live
Longevity
The period of time one is expected to live under ideal circumstances
Lifespan
The period of time in which life events typically occur
